ProgramNode(0...11)(
  [],
  StatementsNode(0...11)(
    [StringConcatNode(0...11)(
       StringNode(0...3)((0...1), (1...2), (2...3), "a"),
       InterpolatedStringNode(5...11)(
         (5...6),
         [EmbeddedStatementsNode(6...10)(
            (6...8),
            StatementsNode(8...9)(
              [CallNode(8...9)(nil, nil, (8...9), nil, nil, nil, nil, 0, "b")]
            ),
            (9...10)
          )],
         (10...11)
       )
     )]
  )
)
